Pension And Postretirement Benefits (Pension And Postretirement Benefit Costs Included In Operating Expenses) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Actuarial (gain) loss	$ (930)	$ 0
Net (credit) cost	(1,196)	(201)
Pension Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost - benefits earned during the period	291	282
Interest cost on benefit obligation	487	484
Expected return on assets	(760)	(783)
Amortization of prior service credit	(30)	(31)
Net (credit) cost	(12)	(48)
Postretirement Benefit [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost - benefits earned during the period	29	41
Interest cost on benefit obligation	191	222
Expected return on assets	(77)	(80)
Amortization of prior service credit	(397)	(336)
Actuarial (gain) loss	(930)	0
Net (credit) cost	$ (1,184)	$ (153)